Biodegradation of anionic and cationic surfactants using bacterial strains from activated sludge

Abstract

Anionic and cationic surfactants are very common pollutants which could be biodegraded by microorganisms during the biological step of the Wastewater Treatment Plant (WWTP) process. During the biodegradation step, the microorganisms use the surfactant as as a source of nutrients breaking down their chemical structure into simpler chemical compounds. There have been data showing that certain surfactants can be completely biodegraded to CO2 and H2O, but there have been also data suggesting that some surfactants were extremely low biodegradable. Their low biodegradability could reside on surfactants negative effects on water’s surface, such as reducing air/water oxygen transfer, lowering the water quality by foam introduction and sorption on solid particles which generate a toxic effect on microorganisms. For these reasons it is necessary to determine the individual biodegradability of each surfactant or each class of surfactants. In this study, we investigate de biodegradability potential of cationic and anionic surfactants and subsequently their effect on microorganisms. The cationic surfactants, quaternary ammonium salts are molecules with at least one long hydrophobic alkyl chain attached to a positively charged nitrogen atom. The properties of the cationic surfactants linked to surface activity, adsorption onto negatively charged solids, biocidal activity, and their reaction with anionic surfactants made them desirable for a large number of applications such as fabric softeners, disinfectants, demulsifies, emulsifiers, wetting agents, and processing aids. Unfortunately, quaternary ammonium salts can harm organisms from the aquatic systems. Alkyl sulfate and alkyl benzenesulfonate are two of the main anionic surfactants used and sold in high amounts because of their wide range utility in different fields such as personal care products, petrochemical production and foaming production. The excessively presence of cationic and anionic surfactants in the environment generates concern due the pollution effects on the ecosystems by affecting both aquatic systems (marine ecosystems and freshwater ecosystems). The study of their biodegradation potential was carried out for 28 days and the results showed a partial biodegradation of surfactants induced by the microbiological community from the activated WWTP sludge.